Internal seal for mercury vapor rectifiers



Aug. 30, 1932. A GAUDENZ| 1,873,960

INTERNAL SEAL FOR MERCURY VAPOR RECTIFIERS Filed lay 8, 1925 llllllll LW)M @Ww Patented Aug. 30, 1932 UNITED STATES PATENT GFFICE `ABTHUB GA-UDENZI, 0F BADEN, SWITZERLAND, ASSIGNOR TO AKTIENGESELLSCHAFT BROWN BOVERI & CIE., 0F BADEN, SWITZERLAND, A JOINT-STOCK COMPANY OF SWITZEBLAN D INTERNAL SEAL FOR MERCURY VAPOR RECTIFIEBS Application led Haya, 1926, Serial No. 107,575, and in Germany Hay 11, 1925.

This invention relates to a feature of construction of mercury vapor rectifiers. It pertains to seals or closures between portions of the apparatus exposed internall to the mercury vapor, heat and vacuum o the ap- Earatus, and has to do primarily with seals et-ween current carrying and insulating members.

The general object of the invention is the provision of a seal effective to close off internal spaces of the vacuum chambery in such fashion as to prevent passage of mercury vapor from one to the other.

A more particular object is the provision of such a seal which will not contribute to back-firing or short circuiting of the arc in the apparatus, to the vdegree that the seals now employed enerally do.

A further obJect is the provision of such a seal especially qualified to resist disintegration by heat and by mercury.

Another object is the provision of such a seal that will permit passage of air, so that the segregated spaces may be exhausted through the same channel.

Another object is the provision of a seal having the characteristics designated above and which does not require close or accurate nishing of the surfaces between which the seal is formed.

Another object is the provision of a seal which is very easily installed.

Other and further objects will be pointed out or indicated hereinafter, or obvious to one skilled in the art upon an understanding of the invention and the problems involved.

In the drawing forming a part of this specification, I show three forms as illustrative of constructions embodying the invention, but it is to be understood that the claims are intended to cover all other constructions in which the principle of the invention claimed is utilized.

I* the drawing,

Fig. 1 is a sectional elevation of an electrode and its mounting, illustrative of those used in mercury vapor rectifiers, various details of the construction being shown diagrammaticall Figs. 2 an 3 are similar sectional elevations of electrode mountings, shown diagramxnatically, and illustrating other constructions of the seal between the elect-rode and its insulator.

The best known jointing material for metal vessels 1n which a high vacuum is to be mainbest heretofore known for intermediate packing between the metallic and insulating parts of the rectifier, even in places where it was not combined with mercury. It now appea rs, however, that the presence of this material at the boundary between the current-carrying and insulating members may be a source of back-fires or short-circuiting of the arc and thus inimical to satisfactory operation. This probably results from the fact that under high and sustained heating it is prone to change form and disintegrate, thus providing in t-he vacuum chamber a dust which has the characteristic of provoking certain conditions productive of back-firing.

In many instances it is desirable to prevent access of mercury vapor to various parts of the apparatus which are enclosed in the vacuum chamber and which it Ais desirable also to maintain in the vacuum. 'For example, it is quite desirable that the spaces around the Shanks or shafts of the iron electrodes within the rectifier casing be maintained free of mercury vapor, so that there will be no condensation of mercury in them, and it is also important that they be easily kept exhausted to the desired vacuum, in

- order that the atmosphere about the head of the electrode be maintained at a minimum density. It is likewise important that the portions of the iron electrode within the rectifier chamber be kept out of contact with lits insulator. The provision of a suitable seal which will fulfill the requirements of such a situation has presented a diflicult problem.

I have discovered and demonstrated that a ver effective seal, fullling the requirements indicated above, may be made of carbon. The carbon may be of various sources, such as graphite, gas carbon, lamp black, etc., but the important prerequisite is that it be as nearly pure as possible. 'I have found the 'best form to be an electrolytic graphite. Of p course, the structural form and manner of application of the seal will vary with the requirements and conditions of -the various situations in which it is installed. Three illustrative examples are shown in the drawing, wherein the seal is formed between the metal anode and its insulator within the vacuum chamber of a mercury vapor rectifier. In these illustrations, the reference character 10 designates a closure portion of the rectifier casing, and the numeral 11 designates a portion of the space within the casinglwhich is maintained under vacuum. The electrode 12 has a headl portion and reduced shaft portion, the latter being in two screw-connected sections housed in a tubular insulator or bushing 14, leaving an intervening space 15,

wherein the' electrode is maintained out of lator is for the purpose of preventing access of mercury vapor from the space 11 into the space 15,' while permitting the latter space to be exhausted. In the form shown in Fig. 1 the interior seal is formed by carbon in pulverulent and granular form. Within the space l5 is a packing of granlar carbon should* be formed to fit the contacting surfaces accurately to avoid breaking under me# chanical pressure. In all instances the car-- bon should be as nearly pure as it can be g made, as the presence of impurities may lead to the occurrences which it is the purpose of the invention to avoid, and which are not induced by the element4 in the pure state.

What I claim is 1 In a mercury vapor rectifier, the combination withan electrode and insulator associated therewith and spaced therefrom, of a body of carbon segregating the space between said electrode and insulator from the rectifier chamber. p Y

2. In a metal vapor rectifier, an electrode having a head and a supporting shaft and being provided therebetween with a shoulder, an insulator disposed about said shaft and spaced therefrom, and a seal of carbonaceous material disposed in the spaces between said Ainsulator and said shaft and Abetween sald boulder and the adjacent endl of said insuator.

In testimony whereof I have hereunto subscribed L-my name at Zurich Switzerland, on the 17 day of March, A. D. 1926.

' ARTHUR GAUDENZI.

20, closely filling the lower portionv of the space between the electrode shaft and the insulator, while between the end of the insulator and the shoulder of the electrode is a layer 20'a of finer carbon, which is held in Y place by the pinching action of those parts induced by the screwing together of the' sections of the electrode. The mass of carbon holds the electrode out of contact'with the I insulator and prevents the passage of mercury vapor into the space 15, but allows the passage of gases out of the latter into the space 11, so that the desired low pressure may be maintained within the insulator. In the form shown in Fig. 2, the seal is provided by a carbon disk 21, between the shoulder of the electrode and the end`of the insulator, while in Fig. 3 is shown a form wherein the seal is provided by a carbon sleeve 22, closely fitting between the inner wall of the insulator and the outer surface of the electrode shaft. In the ,two latter forms, the carbon element 

